Semiconductor device and signal processing method thereof

ABSTRACT

A semiconductor device includes a one-segment tuner I/F that is connected to a one-segment tuner, a tuner I/F that is connected to a digital terrestrial tuner, a decoder that selectively decodes a first broadcast signal supplied from the one-segment tuner I/F and a second broadcast signal supplied from the tuner I/F, a general purpose processor that is provided separately from the decoder and decodes the first broadcast signal, and a switch unit that, based on signal intensity of the second broadcast wave, switches the decoding by the decoder between the first broadcast signal and the second broadcast signal while the general purpose processor is decoding the first broadcast signal. The one-segment tuner I/F, the tuner I/F, the decoder, the general purpose processor, and the switch unit are integrated on one chip.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese patent application No. 2012-058632, filed on Mar. 15, 2012, thedisclosure of which is incorporated herein in its entirety by reference.

The present invention relates to a semiconductor device and a signalprocessing method thereof, and for example, to a semiconductor deviceincluding two tuner I/Fs and a signal processing method thereof.

Japanese Unexamined Patent Application Publication No. 2008-193654discloses a digital broadcast reception circuit that switchesone-segment (hereinafter referred to as 1 seg) broadcasting andtwelve-segment (hereinafter referred to as 12 seg) broadcasting. Forexample, the reception circuit disclosed in Japanese Unexamined PatentApplication Publication No. 2008-193654 starts a decode process of the 1seg broadcasting when a reception status of the 12 seg broadcastingdeteriorates.

SUMMARY

However, the present inventor has found a problem in the techniquedisclosed in Japanese Unexamined Patent Application Publication No.2008-193654 that it is difficult to appropriately switch a receptionprocess. Other issues and new features will be apparent from thedescription in this specification and the drawings attached herewith.

An aspect of the present invention is a semiconductor device thatincludes a first tuner I/F that is connected to a first tuner forturning in a first broadcast wave transferring content data, a secondtuner I/F that is connected to a second tuner for tuning in a secondbroadcast wave transferring the content data, a decoder that selectivelydecodes a first broadcast signal supplied from the first tuner I/F and asecond broadcast signal supplied from the second tuner I/F, a generalpurpose processor that is provided separately from the decoder anddecodes the first broadcast signal, a switch unit that, based on signalintensity of the second broadcast wave, switches the decoding by thedecoder between the first broadcast signal and the second broadcastsignal while the general purpose processor is decoding the firstbroadcast signal. Further, the first tuner I/F, the second tuner I/F,the decoder, the general purpose processor, and the switch unit areintegrated on one chip.

According to the above aspect, it is possible to provide a semiconductordevice, a navigation system, and a signal processing method that canappropriately switch a reception process.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, advantages and features will be moreapparent from the following description of certain embodiments taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram showing a configuration of a semiconductordevice according to a first embodiment;

FIG. 2 is a block diagram for explaining reception switch by thesemiconductor device;

FIG. 3 is a block diagram for explaining reception switch by thesemiconductor device;

FIG. 4 is a block diagram for explaining reception switch by thesemiconductor device;

FIG. 5 is a block diagram for explaining reception switch by thesemiconductor device;

FIG. 6 explains an operation of the reception switch; and

FIG. 7 is a block diagram showing a configuration of a navigation systemusing a semiconductor device according to a second embodiment.

DETAILED DESCRIPTION First Embodiment

Hereinafter, embodiments of the present invention are explained withreference to the drawings. FIG. 1 is a block diagram showing aconfiguration of a semiconductor device 10 according to this embodiment.The semiconductor device 10 includes a general purpose processor 11, a 1seg tuner I/F (interface) 12, a decoder 13, a demultiplexer 14, and atuner I/F (interface) 15. The semiconductor device 10 is connected to a1 seg tuner 51 and a digital terrestrial tuner 52. The general purposeprocessor 11 includes a switch unit 16 and a decode unit 17.

Each block is provided as an IP (Intellectual Property) core, forexample. The semiconductor devices 10 is an LSI (Large Scale Integratedcircuit), such as SoC (System on Chip), and the abovementionedcomponents are integrated on one chip. For example, the semiconductordevice 10 composes a control semiconductor chip for a car navigationsystem mounted on a motor vehicle. The semiconductor device 10 is usedfor a receiver that receives digital terrestrial TV broadcasting.Further, the semiconductor device 10 switches the 1 seg broadcasting andthe 12 seg broadcasting and receives broadcast waves.

The 1 seg tuner (first tuner) 51 receives 1 seg broadcast waves (firstbroadcast waves) of the digital terrestrial TV broadcasting and tunestherein. The 1 seg tuner 51 is connected to the 1 seg tuner I/F 12. The1 seg tuner 51 outputs 1 seg broadcast signals (first broadcast signals)based on tuned 1 seg broadcast waves to the 1 seg tuner I/F (first tunerI/F) 12.

The digital terrestrial tuner (second tuner) 52 receives 12 seg (alsoreferred to as 12-segment and full segment) broadcast waves (secondbroadcast waves) and tunes therein. The digital terrestrial tuner 52 isconnected to the tuner I/F (second tuner I/F) 15. The digitalterrestrial tuner 52 outputs 12 seg broadcast signals (second broadcastsignals) based on the tuned 12 seg broadcast waves to the tuner I/F 15.Note that although each tuner has a demodulation function, a demodulatorfor demodulating the digital terrestrial broadcast signals and the 1 segbroadcast signals may be included in the semiconductor device 10instead.

In the digital terrestrial TV broadcasting, information for one channelis divided into 13 segments to be transmitted. Twelve segments of themare used for high-definition (for example, resolution of 1920×1080pixels at 30 frames/sec) television broadcasting (12 seg), and theremaining one segment is used for the 1 seg broadcasting (for example,resolution of 320×240 at 15 frames/sec). In this example, the 1 segbroadcast waves and 12 seg broadcast waves transfer the same contentdata with different resolution and frame rates. That is, the datatransferred on the 1 seg broadcast waves is smaller than the datatransferred on the 12 seg broadcast waves. Further, the 1 seg tuner 51and the digital terrestrial tuner 52 tune in the same channel.

The demultiplexer 14 demultiplexes the 1 seg broadcast signals or the 12seg broadcast signals. For example, the demultiplexer 14 separates astream of broadcast signals into a video stream and a voice stream. Thedecoder 13 is an IP (Intellectual Property) core dedicated for decodeprocesses and selectively decodes the digital terrestrial broadcastsignals and the 1 seg broadcast signals. For example, the decoder 13decodes the broadcast signals separated into the video stream and theaudio stream by the demultiplexer 14. Specifically, the decoder 13decodes an image and audio compressed in accordance with the standardsuch as H.264 and MPEG4. Then, the decoded video or audio signals areoutput to a monitor or a speaker not shown. This enables TV content ofthe digital terrestrial broadcasting to be displayed on the monitor.Note that several frames of overhead are necessary for interframeinterpolation in H.264 and MPEG4.

Hereinafter, a signal processing method of the semiconductor device 10according to this embodiment is explained using FIGS. 1 to 6. FIGS. 2 to5 are block diagrams of the semiconductor device 10 for explaining aprocess flow and are similar to the block diagram of FIG. 1. FIG. 6shows changes in field intensity of the 12 seg broadcast waves andswitches of the decode operation.

When the field intensity of the 12 seg broadcast waves is sufficient,the decoder 13 decodes only the 12 seg broadcast signals (period A inFIG. 6). At this time, the decoder 13, the demultiplexer 14, the tunerI/F 15, and the digital terrestrial tuner 52 operate and decode the 12seg broadcast signals (see the dotted rectangle in FIG. 1). In theperiod A in FIG. 6, the general purpose processor 11 is not performingthe decode process, thus the general purpose processor 11 can performother processes. Thus, the process load of the general purpose processor11 can be reduced.

When the field intensity of the 12 seg broadcast wave falls below afirst threshold, the general purpose processor 11 starts up the decodeprocess of the 1 seg broadcast signals (period B in FIG. 6). Then, thedecoding unit 17 in the general purpose processor 11 decodes the 1 segbroadcast signals transmitted from the 1 seg tuner 51 to the 1 seg tunerI/F 12. In this example, the general purpose processor 11 and the 1 segtuner I/F 12 operate and decode the 1 seg broadcast signals from the 1seg tuner 51 (see the dotted rectangle in FIG. 2). In the period B inFIG. 6, decoding of the 12 seg broadcast signals by the decoder 13 anddecoding of the 1 seg broadcast signals by the general purpose processor11 is performed in parallel. That is, the semiconductor device 10simultaneously decodes the 12 seg broadcast signals and the 1 segbroadcast signals. Therefore, the compressed image data in a specificperiod is decoded by both the general purpose processor 11 and thedecoder 13. Note that the general purpose processor 11 demultiplexes the1 seg broadcast signals when the general purpose processor 11 isdecoding the 1 seg broadcast signals. While the general purposeprocessor 11 and the decoder 13 simultaneously decode, the monitordisplays content based on the 1 seg broadcast signals decoded by thegeneral purpose processor 11.

For example, the switch unit 16 provided in the general purposeprocessor 11 compares the field intensity of the 12 seg broadcast wavesand the first threshold. Then, the switch unit 16 outputs a signalindicating a comparison result to the general purpose processor 11, thedecoder 13 and the like. When the field intensity of the 12 segbroadcast waves is greater than the first threshold, only the decodingof the 12 seg broadcast signal by the decoder 13 is performed. When thefield intensity of the 12 seg broadcast waves falls below the firstthreshold, the decode unit 17 in the general purpose processor 11 startsdecoding the 1 seg broadcast signals. In this way, the general purposeprocessor 11 determines whether or not to decode the 1 seg broadcastsignals according to the comparison result between the field intensityof the 12 seg broadcast waves and the first threshold. Note that in theperiod B in FIG. 6, the decoding of the 12 seg broadcast signals by thedecoder 13 is performed together with the decoding of the 1 segbroadcast signals by the general purpose processor 11.

Next, when the field intensity of the 12 seg broadcast waves falls belowa second threshold, the display switches from the 12 seg broadcasting tothe 1 seg broadcasting (boundary between the periods B and C in FIG. 6).That is, when the field intensity falls to a non-viewable region, themonitor display switches from the 12 seg broadcasting to the 1 segbroadcasting. As the general purpose processor 11 is already decodingthe 1 seg broadcast signals, seamless switching of the broadcasting canbe achieved.

Then, the decoder 13 performs switch setting from the 12 segbroadcasting to the 1 seg broadcasting (period C in FIG. 6).Specifically, the decoder 13 stops decoding the 12 seg broadcastsignals, and performs a setup operation for decoding the 1 seg broadcastsignals. To this end, the decoder 13 reads the configuration requiredfor decoding the 1 seg broadcast signals. The monitor displays thecontent based on the 1 seg broadcast signals decoded by the decode unit17 in the general purpose processor 11 even during the setup operationof the decoder 13.

More specifically, the switch unit 16 compares the second threshold(alert level for fuzzy video) and the field intensity of the 12 segbroadcast waves. Then, the switch unit 16 outputs the signal indicatingthe comparison result to the general purpose processor 11, the decoderand the like. When the field intensity of the 12 seg broadcast wavesfalls below the second threshold, the broadcasting is switched to the 1seg broadcasting. Specifically, the monitor displays the content of the1 seg broadcasting. Note that the second threshold is less than thefirst threshold.

Further, when the switch setting of the decoder 13 is completed, thedecoder 13 starts up the decode process of the 1 seg broadcast signals(period D in FIG. 6). Note that also in the periods C and D in FIG. 6,the general purpose processor 11 is decoding the 1 seg broadcastsignals. Accordingly, the compressed image data included in the 1 segbroadcast signals is decoded by the general purpose processor 11.

When the decoder 13 starts decoding the 1 seg broadcast signals(boundary between the periods D and E in FIG. 6), the monitor displaysthe content based on the 1 seg broadcast signals decoded by the decoder13 (period E in FIG. 6). At this time, the decode unit 17 in the generalpurpose processor 11 stops the decode process. For example, when thedecoder 13 starts up the decode process of the 1 seg broadcast signals,the decoder 13 transmits a signal indicating of the ongoing decodeprocess of the 1 seg broadcast signals to the general purpose processor11. Then, while the monitor displays the content based on the 1 segbroadcast signals decoded by the decoder 13, the general purposeprocessor 11 stops the decode process of the 1 seg broadcast signals. Byproviding the period for simultaneous decoding in the abovementionedmanner, it is possible to seamlessly switch the broadcasting even in thecase there are several frames of overhead. That is, as the decoding isperformed for one of 1 seg and 12 seg broadcast signals at all times, itis possible to eliminate time when the monitor is unable to display thecontent.

In this example, as shown in FIG. 4, the 1 seg broadcast signals fromthe 1 seg tuner I/F 12 are supplied to the demultiplexer 14. Then, thedecoder 13 decodes the 1 seg broadcast signals demultiplexed by thedemultiplexer 14. In the period E in FIG. 6, the general purposeprocessor 11 is not performing the decode process. This reduces theprocess load of the general purpose processor 11 and enables the generalpurpose processor 11 to perform other processes than the decode process.

Note that after the field intensity falls below the first threshold,when the field intensity returns greater than or equal to the firstthreshold without falling below the second threshold, the generalpurpose processor 11 stops the decode process of the 1 seg broadcastsignals. That is, in such a case, after the general purpose processor 11starts decoding the 1 seg broadcast signals, the decoder 13 will notdecode the 1 seg broadcast signals. In other words, the monitor will notdisplay the content based on the 1 seg broadcast signals decoded by thegeneral purpose processor 11 and continue to display the content of the12 seg broadcasting decoded by the decoder 13.

On the other hand, when the field intensity of the 12 seg broadcastwaves returns to the second threshold after falling below the secondthreshold (boundary between the periods E and F in FIG. 6), the generalpurpose processor 11 starts up the decode process of the 1 seg broadcastsignals (period F in FIG. 6). Then, as shown in FIG. 5, the generalpurpose processor 11 decodes the 1 seg broadcast signals supplied fromthe 1 seg tuner 51 to the 1 seg tuner I/F 12. More specifically, theswitch unit 16 compares the field intensity of the 12 seg broadcastwaves and the second threshold. After that, the switch unit 16 outputs asignal indicating the comparison result to the general purpose processor11 and the decoder 13. When the field intensity of the 12 seg broadcastwaves exceeds the second threshold, the general purpose processor 11starts decoding the 1 seg broadcast signals.

When the general purpose processor 11 completed to start up the decodeprocess of the 1 seg broadcast signals, the decoder 13 performs switchsetting of the decode process. That is, after the general purposeprocessor 11 starts up the decode process, the monitor displays thecontent based on the 1 seg broadcast signals decoded by the generalpurpose processor 11. As described above, while the decoder 13 decodesthe 1 seg broadcast signals, the general purpose processor 11 startsdecoding the 1 seg broadcast signals. This allows seamless switching.

Then, the decoder 13 starts the decode process of the 12 seg broadcastsignals. To this end, the decoder 13 reads the configuration requiredfor decoding the 12 seg broadcast signals. During the setup operation ofthe decoder 13, the decoding unit 17 in the general purpose processor 11is decoding the 1 seg broadcast signals. The decoder 13 starts up thedecode process of the 12 seg broadcast signals and decodes the 12 segbroadcast signals. Accordingly, the decoding of the 12 seg broadcastsignal by the decoder 13 and the decoding of the 1 seg broadcast signalsby the general purpose processor 11 is performed in parallel. When thefield intensity of the 12 seg broadcast signals exceeds the firstthreshold (boundary between the periods F and G in FIG. 6), the monitordisplays the content based on the 12 seg broadcast signals decoded bythe decoder 13. In addition, the general purpose processor 11 ends thedecode process. The switch unit 16 switches the decoding according tothe comparison result between the signal intensity of the digitalterrestrial broadcast waves and the thresholds.

Note that the field intensity may fall to the second threshold afterexceeding the second threshold without returning to the first threshold.In this case, when the field intensity falls below the second threshold,the decoder 13 starts up the decode process of the 1 seg broadcastsignals in a similar manner as in the periods C and D in FIG. 6. Then,after the decoder 13 starts decoding the 1 seg broadcast signals, thegeneral purpose processor 11 stops the decode process as in the periodE.

As described above, when the field intensity of the 12 seg broadcastsignals is between the first threshold and the second threshold, thegeneral purpose processor 11 and the decoder 13 are controlled toperform the decode process in parallel. In other words, as the generalpurpose processor 11 decodes the 1 seg broadcast signals, a period isprovided for decoding the 12 seg broadcast signals and the 1 segbroadcast signals simultaneously. When the field intensity falls belowthe second threshold in the period of simultaneous decoding, the monitordisplay is switched. That is, the monitor display is switched from the12 seg broadcast signals to the 1 seg broadcast signals. On thecontrary, when the field intensity exceeds the first threshold in theperiod of simultaneous decoding, the monitor display is switched fromthe 1 seg broadcast signals to the 12 seg broadcast signals. This allowsseamless switching of broadcasting. Further, when the field intensity ofthe 12 seg broadcast signals is greater than the first threshold orlower than the second threshold, the general purpose processor 11 stopsthe decode process. This reduces the period of simultaneous decoding andthereby also reduces the power consumption. Then, the process load ofthe general purpose processor 11 can be reduced.

The general purpose processor 11 can decode the 1 seg broadcast signalsand unable to decode the 12 seg broadcast signals. To put it anotherway, it is not necessary for the general purpose processor 11 to have adecoding function of the 12 seg broadcast signals. This eliminates theneed for providing the general purpose processor 11 with high throughputfor the decode process. That is, the general purpose processor 11 withhigh throughput is no longer necessary, and thus achieving reduction inthe cost. Additionally, the general purpose processor 11 that performsprocesses other than the decoding will not perform the decode process ofthe 12 seg broadcast signals, which imposes heavy processing load,thereby preventing an increase in the power consumption.

Since the general purpose processor 11 does not decode the 12 segbroadcast signals, it is possible to prevent a bus band from beingoccupied. For example, when a general purpose CPU decodes the 12 segbroadcast signals, 500 MB/sec of the bus band is occupied. In thisembodiment, as the general purpose processor 11 decodes only the 1 segbroadcast signals, necessary bus band is only 16.1 MB/sec. This achievesreduction in the cost of the semiconductor device 10.

Further, only one dedicated decoder IP provided in the semiconductordevice 10 enables appropriate switching of broadcasting. When thedecoder 13 switches the decoding, the general purpose processor 11 isdecoding the 1 seg broadcast signals. In the region or state with lowsignal intensity of the 12 seg broadcast waves, the content is displayedbased on the 1 seg broadcast waves. This prevents frame dropping by theoverhead at the time of switching and enables seamless switching ofbroadcasting. Additionally, as only one decoder 13 needs to be provided,an increase in the size of SoC can be prevented. Moreover, an externalLSI is no longer necessary, thus the cost can be reduced. Furthermore,the decoder 13 can be composed of a dedicated decoder IP, therebysuppressing the increase in the power consumption of the decoder 13 fordecoding the 12 seg broadcast signals.

Only an input terminal provided in the semiconductor device 10 forreceiving a field intensity signal indicating the signal intensity ofthe digital terrestrial broadcast waves enables switching of thebroadcasting. Therefore, simple configuration can achieve easy broadcastswitching. The first and second thresholds may be changed asappropriate. This achieves more appropriate broadcast switching.

Incidentally, fluctuation in the field intensity of the 12 seg broadcastwaves near the threshold leads to frequent switching processes. Thefield intensity of the 12 seg broadcast waves repeatedly exceeds orfalls below the thresholds in a short cycle. This leads to frequentswitching processes, and therefore an increase in the power consumption.In order to prevent such frequent switching, it is preferable to use asignal obtained by integrating the field intensity of the 12 segbroadcast waves as a signal intensity signal. That is, the fieldintensity of the 12 seg broadcast waves is integrated for a certain timeto suppress the fluctuation in the signal intensity signal.

Second Embodiment

As mentioned above, changing the first and second thresholds enablesmore appropriate broadcast switching. For example, the thresholds may bechanged according to whether a motor vehicle with a car navigationsystem mounted thereon that includes the semiconductor device of thisembodiment is travelling in a city or a mountain area. In addition, thethresholds may be changed according to the speed of the motor vehicleand weather. By the semiconductor device of this embodiment used in acontrol semiconductor chip for controlling the navigation system, it ispossible to switch the broadcasting more appropriately. In this way, thesemiconductor device of this embodiment used as the control chip for thenavigation system achieves more appropriate switching.

Hereinafter, a configuration of the semiconductor device used as thecontrol chip for the navigation system is explained with reference toFIG. 7. FIG. 7 is a block diagram showing a configuration of a controlsystem of a navigation system 100 according to this embodiment. Notethat the signal processing for switching the broadcasting is similar tothe first embodiment, thus the explanation will not be repeated here.That is, processes other than changing the thresholds are similar to thefirst embodiment.

A semiconductor device 101 includes a general purpose CPU 111, a decoder113, a demultiplexer 114, a tuner I/F 115, a graphic module 121, adisplay control module 122, a video input module 123, an audio DSP(Digital Signal Processor) 124, a MOST (Media Oriented System Transport)module 125, an SATA (Serial Advanced Technology Attachment) module 126,a USB (Universal Serial Bus) module 127, a DDR controller 128, a systembus 130, an image recognition module 134, a GPS (Global PositioningSystem) module 135, an FM VICS® (Frequency Modulation VehicleInformation and Communication System) module 136, a CAN module 137, aSpeed module 138, a GPIO (General Purpose Input Output) 139, a 1 segtuner I/F 112, a peripheral bus 140, a CPG (Clock Pulse Generator)module 141, a timer 142, a serial I/F 143, a parallel I/F 144, an SDcard I/F 145, and a sound I/F 146. Note that each module of thesemiconductor device is configured as an IP core, for example.

The decoder 113 corresponds to the decoder 13 of the first embodimentand selectively decodes the 1 seg broadcast signals and 12 seg broadcastsignals. The decoder 113 includes a video codec 131, an image enhancer132, and an IPC (Interlace Progressive Conversion) module 133. Thegeneral purpose CPU 111 corresponds to the general purpose processor 11of the first embodiment and is a control processor of the navigationsystem. The general purpose CPU 111 includes a navigation and OSprocessing block 118 and a media processing block 119. Note that the OSis Windows®, Linux®, iTron and the like.

The navigation and OS processing block 118 entirely controls each module(block) regarding the navigation mentioned later. That is, a navigationfunction is realized by comprehensive control on the later mentionedmodules by the navigation and the OS processing block 118. For example,the navigation and the OS processing block 118 displays a currentposition of a travelling motor vehicle on a map displayed on the liquidcrystal display monitor 161. Further, the navigation and the OSprocessing block 118 performs setting of a destination and processesconcerning route finding and the like.

The media processing block 119 entirely controls the modules (blocks)regarding the digital terrestrial broadcasting. That is, as the mediaprocess block 110 comprehensively controls the later mentioned modules,the content of the digital terrestrial broadcasting can be displayed onthe liquid crystal display monitor 161. For example, the mediaprocessing block 119 displays on the liquid crystal display monitor 161video of content broadcasted in the digital terrestrial broadcasting andoutputs audio of the content broadcasted in the digital terrestrialbroadcasting from a speaker not shown. The media processing block 119functions as the decoder 13 and the switch unit 16 of the firstembodiment.

The liquid crystal display monitor 161, a camera 162, a DDR memory 129,and a tuner 152 are provided in the navigation system 100. The liquidcrystal display monitor 161, the camera 162, the DDR memory 129, thetuner 151, and the tuner 152 are connected to the semiconductor device101 and controlled by the general purpose CPU 111. The camera 162 is,for example, a camera for rear view that is mounted on the motorvehicle. The liquid crystal display monitor 161 is a monitor fordisplaying a map of the navigation system or an image and the likecaptured by the camera 162. Not to mention that the liquid crystaldisplay monitor 161 may be other monitors such as an organicelectroluminescence monitor.

The tuner 151 is similar to the abovementioned 1 seg tuner I/F 12 andtunes in the 1 seg broadcast waves. The tuner 152 is similar to thetuner I/F 15 of the first embodiment and tunes in the 12 seg broadcastwave. Note that the navigation system 100 includes a plurality of tuners152. Therefore, the navigation system 100 also has a plurality of tunerI/Fs 115. The tuners 151 and 152 may demodulate the 12 seg broadcastwaves and the 1 seg broadcast waves, or a demodulator may be providedseparately.

The graphic module 121 is a graphic engine that performs processes forgenerating display data to be displayed on the liquid crystal displaymonitor 161. The graphic module 121 generates data for navigation mapsfrom map information stored to an SD card, a DVD-ROM, or a hard diskdrive. The display control module 122 generates display signals based onthe display data generated by the graphic module 121 and outputs thedisplay signals to the liquid crystal display monitor 161. Then, theliquid crystal display monitor 161 displays a desired image. The videoinput module 123 receives data captured by the camera 162. The audio DSP124 performs digital signal processing for outputting and inputtingaudio data.

The MOST module 125 is connected to MOST mounted on the motor vehicle.The MOST builds a network for connecting onboard multimedia devices. TheMOST module 125 performs processes to signals output to MOST or signalsreceived from MOST. The SATA module 126 is connected to the variousdrives including a hard disk drive, an optical disk drive and the like.The SATA module 126 performs processes to signals output to the variousdrives or the signals received from the various drives. The USB module127 is connected to a USB device such as a USB memory. The USB module127 performs processes to signals output to the USB device or signalsreceived from the USB device.

The DDR controller 128 controls reading and writing process from and tothe external DDR (Double Data Rat) memory 129. The DDR controller 128writes, for example, the map information and content information to theDDR memory 129 or reads the information from the DDR memory 129. Thedecoder 113 corresponds to the decoder 13 of the first embodiment andselectively decodes the 12 seg broadcast signals and 1 seg broadcastsignals. The decoder 113 includes the video codec 131, the imageenhancer 132, and the IPC module 133. The video codec 131 encodes anddecodes video data. The image enhancer 132 performs image processing tothe decoded image and reduces jaggies. The IPC module 133 converts aninterlaced signal into a progressive signal.

The GPS module 135 locates positions based on the signals from a GPSsatellite. Then, the position coordinates of the motor vehicle with thecar navigation system mounted thereon are measured. The FM VICS® module136 performs processes to VICS® information received by an FM antenna(not shown) and outputs the processed information to the graphic module121. Then, the VICS® information can be displayed on the liquid crystaldisplay monitor 161. The image recognition module 134 is an imagerecognition engine that performs an image recognition process to theimage captured by the camera 162. For example, the image recognitionmodule 134 performs a process to the image captured by the camera 162 inorder to recognize lanes, street signs and the like.

The CAN module 137 is connected to CAN mounted on the motor vehicle. CANbuilds a network concerning cruise control of the motor vehicle. The CANmodule 137 performs processes to signals output to CAN or the signalsreceived from CAN. The Speed module 138 receives vehicle speed pulsesfrom the motor vehicle and calculates the speed of the motor vehiclebased on the vehicle speed pulses. The travelling speed of the motorvehicle can be obtained in this way. The current position of the motorvehicle may be estimated based on the vehicle speed of the motor vehicledetected by the Speed module 138. The GPIO 139 includes an input andoutput terminal and is an interface with an external device. Forexample, the field intensity signal is supplied to the GPIO 139 from thetuner 152.

The CPG module 141 generates a clock pulse and outputs the clock pulseto each module as appropriate. When the process load of the generalpurpose CPU 111 increases, the timer 142 will be a timer for terminatingthe general purpose CPU 111 and performing an interruption process. Theserial I/F 143 will be an interface such as operation buttons for aninput and output device. The parallel I/F 144 will be an interface forthe DDR memory 129, RAM and the like. The SD card I/F 145 is aninterface for an SD card inserted into a card slot. The sound I/F 146will be an interface for a microphone and a speaker not shown. Thus,audio signals of navigation guidance and the content are output from thesound I/F 146 to the speaker not shown. Each of the abovementionedblocks (modules) is connected via the system bus 130 or the peripheralbus 140, and the signals are transmitted and received via the buses.

Further, in a similar manner as the first embodiment, control fordisplaying the digital terrestrial broadcasting is performed.Specifically, the semiconductor device 101 switches the decode processaccording to the signal intensity of the 12 seg broadcast waves. Forexample, when the signal intensity of the 12 seg broadcast waves is low,the content transferred in the ground digital broadcasting is displayedbased on the 1 seg broadcast waves. At the time of switching thedecoding by the decoder 113 from the 12 seg broadcast signals to the 1seg broadcast signals, in a similar manner as the first embodiment, thedecoding of the 1 seg broadcast signals by the general purpose CPU 111and the decoding of the 12 seg broadcast signals by the decoder 113 isperformed simultaneously. Similarly, at the time of switching thedecoding by the decoder 113 from the 1 seg broadcast signals to the 12seg broadcast signals, in a similar manner as the first embodiment, thedecoding of the 1 seg broadcast signals by the general purpose CPU 111and the decoding of the 12 seg broadcast signals by the decoder 113 isperformed simultaneously. Then, it is possible to achieve the sameadvantages as the first embodiment. Note that as the switching controlis similar to that of the first embodiment, detailed explanation willnot be repeated here.

Moreover, in this embodiment, the thresholds used for switching thedecode process are changed as appropriate. That is, the first thresholdfor evaluating whether or not to perform the decoding by the generalpurpose CPU 111 and the second threshold for evaluating whether or notto switch the decoding by the decoder 113 are changed. Arbitrarilychanging the thresholds allows the semiconductor device 101 toappropriately switch the decode process.

The thresholds may be switched depending on the location positioned bythe GPU module 135 and the like. For example, the GPS module 135evaluates whether the motor vehicle is in a city or a suburban area withreference to the map information of the navigation system. The signalintensity of the 12 seg broadcast waves tends to fall, for example, incities surrounded by multistory buildings, tunnels, and mountainousareas due to obstacles. Therefore, such places where the signalintensity falls are registered to the map information beforehand. Thethresholds are changed when the motor vehicle enters the previouslyregistered area. For example, the thresholds are changed higher in theplace where the signal intensity tends to fall due to the obstacles. Inthis way, the content is displayed based on the 1 seg broadcast wavesthat provide wider reception area in the place that tends to have lowersignal intensity. Moreover, the broadcasting is interrupted near theborder between prefectures, for instance, where broadcast channelsswitch. Therefore, the thresholds are changed higher near the borderbetween prefectures in order to decode the 1 seg broadcast signals withwider reception area. As has been explained, the thresholds can bechanged with reference to the map information of the navigation systemand the current position of the motor vehicle.

Furthermore, temperature information and weather information may beacquired from OS, and the thresholds may be changed higher or lowerdepending on the information. For example, as the signal intensity ofthe 12 seg broadcast waves falls in fog, the thresholds are changedhigher. Therefore, the decoding can be switched to the 1 seg broadcastsignals. Alternatively, the thresholds may be changed according totemperature, ultraviolet rays (sunlight) and the like.

In addition, the thresholds may be adjusted according to the speedacquired by the Speed module 138. For example, the motor vehicle canstably receive the broadcast waves while travelling at a low speed. Insuch a case, the thresholds may be reduced. Moreover, when the motorvehicle travels at a high speed, the broadcasting may not be switchedupon instantaneous wave interruption. As described so far, thethresholds are preferably changed according to at least one of thetemperature information, the weather information, the speed information,and the position information that is supplied to the processor. Thisallows the semiconductor device 101 to appropriately switch the decodingprocess according to the travelling environment.

Incidentally, the signal intensity may instantaneously change by noise.Upon such an instantaneous change in the signal intensity, it ispreferable to control the general purpose CPU 111 not to perform thedecode process. This contributes to further reduction in the powerconsumption. In other words, the power consumption increases by thegeneral purpose CPU 111 starting the decode process at every suddenchange in the signal intensity. This increases the number of times forthe general purpose CPU 111 to start the decode process. Consequently,there may be excessive simultaneous decoding by the general purpose CPU111 and the decoder 113. For this reason, it is preferable that thegeneral purpose CPU 111 is prevented from starting the decode processwhen the signal intensity is instantaneously reduced by noise. In orderto do that, the integrated value of the field intensity and thethresholds are compared. Then, the power consumption can be reduced.This further reduces the process load of the general purpose CPU 111.

The reception environment of the broadcast waves may change along with amovement of the motor vehicle. There are a case when the motor vehiclemoves from an environment with high field intensity to an environmentwith low field intensity and a case when the motor vehicle moves fromthe environment with low field intensity to the environment with highfield intensity. In particular, the reception status of the in-vehicledevices may instantaneously improve or deteriorate due to the hightravelling speed of the motor vehicle. In order to deal with this issue,the general purpose CPU 111 integrates the field intensity in immediatecertain period of time. Then, the integrated value and the thresholdsare compared to control switching of the broadcasting. This enablesprevention of switching caused by temporary noise and an influence ofdisturbances including geographical feature and wave interruption byobstacles. Further, in the case of instantaneous deterioration of thereception status, a video processing engine operating in the generalpurpose CPU 111 is controlled to drop frames, for example. This allowsprevention of sudden switch between the 12 seg broadcasting and the 1seg broadcasting.

Furthermore, as the noise, there are circuit noise and environmentalnoise. The circuit noise is generated inside the semiconductor device101. That is, the input field intensity may change due to noise in theI/F units and internal circuits even when the reception environment ofthe broadcast waves remains unchanged. The integrated value of the fieldintensity signal and the thresholds are compared in order to preventswitching of the decode process due to the circuit noise. Then, thecircuit noise can be detected, and thereby preventing an erroneouschange of the operating state.

As the environmental noise, there is instantaneous fluctuation in thefield intensity by the obstacles, geographical features, weather, andtravelling speed, as mentioned above. When the motor vehicle moves fromthe environment with high field intensity to the environment with lowfield intensity, only the preparation for the decode process by thegeneral CPU 111 is performed. When the integrated value continues todecrease and falls to less than or equal to the first threshold, thegeneral purpose CPU 111 starts the decode process. In the case of themovement from the environment with low field intensity to theenvironment with high field intensity, the general purpose CPU 111prepares for the decode process upon a sudden increase in the fieldintensity. When the integrated value continues to increase, the decoderstarts up the decode process of the 12 seg broadcast signals. When theintegrated value exceeds the first threshold, the general purposeprocessor 11 ends the decode process.

Note that the semiconductor device according to this embodiment may bemounted on a navigation system other than the car navigation systemmounted on the motor vehicle. For example, the semiconductor device canbe mounted on cellular phones including smartphones.

TV broadcasting system depends on a country. For example, ISDB-T(Integrated Services Digital Broadcasting-Terrestrial) is used for thesecond broadcasting waves and a part of ISDB-T is used for the firstbroadcasting waves in Japan. In Europe, DVB-T (Digital VideoBroadcasting-Terrestrial) is used for the second broadcasting waves andDVB-H (Digital Video Broadcasting-Handheld) is used for the firstbroadcasting waves. In South America counties such as Brazil, ISDB-TB isused for the second broadcasting waves and a part of ISDB-TB is used forthe first broadcasting waves. In South Korea, ATSC (Advanced TelevisionSystems Committee) standards is used for the second broadcasting wavesand T-DMB (Terrestrial-Digital Media Broadcasting) is used for the firstbroadcasting waves. In China, CDMB (China Digital Multimediabroadcasting)-T is used for the second broadcasting waves and CMMB(China Mobile Multimedia broadcasting) is used for the firstbroadcasting waves. In the United States, ATSC is used for the secondbroadcasting waves. In Middle East, Southeastern Asia, South Africa,Australia and so on, DVB-T is used for the second broadcasting waves andDVB-H is used for the first broadcasting waves. It is possible to selectthe compliant broadcasting system based on the country where thesemiconductor device is used. The semiconductor device decodes the firstand second broadcasting waves in accordance with the broadcastingsystem. As a matter of course, another broadcasting system may be usedfor first broadcasting waves or the second broadcasting waves.

The first and second embodiments can be combined as desirable by one ofordinary skill in the art.

Note that the present invention is not limited to the above embodimentsbut may be changed as appropriate within the range not departing fromthe scope.

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention can bepracticed with various modifications within the spirit and scope of theappended claims and the invention is not limited to the examplesdescribed above.

Further, the scope of the claims is not limited by the embodimentsdescribed above.

Furthermore, it is noted that, Applicant's intent is to encompassequivalents of all claim elements, even if amended later duringprosecution.

What is claimed is:
 1. A semiconductor integrated circuit deviceprovided in a semiconductor chip, comprising: a first tuner interfaceconfigured to be coupled to a first tuner for receiving a firstbroadcast wave transferring first content data; a second tuner interfaceconfigured to be coupled to a second tuner for receiving a secondbroadcast wave transferring second content data; a general purposeprocessor configured to decode a first broadcast signal supplied fromthe first tuner interface; and a decoder configured to decode the firstbroadcast signal and a second broadcast signal supplied from the secondtuner interface, wherein an amount of the first content data transferredper unit time is smaller than that of the second content data, whereinthe general purpose processor and the decoder are configured to decodethe first broadcast signal and the second broadcast signal,respectively, in a same period, and wherein the general purposeprocessor has a function of determining which of the first and secondbroadcast signals the decoder decodes based on a field intensity of thesecond broadcast wave.
 2. The semiconductor integrated circuit deviceaccording to claim 1, wherein the general purpose processor starts todecode the first broadcast signal when a field intensity of the secondbroadcast wave falls below a first threshold level, and wherein thedecoder starts to decode the first broadcast signal when a fieldintensity of the second broadcast wave falls below a second thresholdlevel which is lower than the first threshold level.
 3. Thesemiconductor integrated circuit device according to claim 2, whereineach of the first and second threshold levels is variable.
 4. Thesemiconductor integrated circuit device according to claim 3, whereinthe general purpose processor is a control processor of an on-boardnavigation system, and wherein the first and second threshold levelschange according to at least one of weather information, speedinformation, and position information supplied to the general purposeprocessor.
 5. The semiconductor integrated circuit device according toclaim 1, wherein the first and the second tuners are components of theon-board navigation system.
 6. The semiconductor integrated circuitdevice according to claim 1, wherein the semiconductor integratedcircuit device is configured to be employed in a car navigation system.7. The semiconductor integrated circuit device according to claim 1,wherein the semiconductor integrated circuit device is configured to beemployed in a mobile phone.
 8. The semiconductor integrated circuitdevice according to claim 1, wherein the general purpose processor andthe decoder are configured to decode the first broadcast signal and thesecond broadcast signal simultaneously in the same period.